lower boost

[gvig]

For a long time my wastegate has been stuck closed, and I left it that way on purpose. I managed my boost by managing my throttle. I had to watch it though because under full throttle I could manage 20 to 22 pounds. When I saw that much boost I would rapidly reduce throttle to reduce boost.

I just removed the vacuum pump and made a manual boost control for the turbo and I freed the wastegate. Now I have dramatically lower boost, at partial throttle where I would have had say, 6 or 8 pounds it is now several pounds lower even though total boost is set at 13 under full throttle.

Is that to be expected?

I would have thought that the boost would be the same until up to a point near where the wastegate starts to open. What is wrong with my thinking??

[More Power]

The PCM is managing boost pressure in ways that go well beyond just max boost (like a spring loaded actuator). Boost pressures diminish as rpms increase. Max boost is designed to occur at 1800-2000 rpm. My guess is that the engineers wanted the wastegate to open at higher rpms to help reduce exhaust backpressures and to reduce stress on the engine as dynamic forces increase.

Jim

[gvig]

Thanks Jim, I guess the truck is smarter than I am! My comparison though was of a stuck wastegate versus a spring loaded wastegate.

It is for sure the PCM is smarter than I am.

I have now driven the truck a bit and the boost is back like I thought it should be, up till the wastegate opening begins. I guess that when I manually opened the gate that had been stuck (just really stiff, not physically jammed) for so many months I may have dislodged some carbon (now where would that come from?) that may have caught in the gate and kept it from truly sealing off when closed, thus spillage and less pressure.

All is well now, thanks for the answer.

[DA BIG ONE]

On my burb w/gate closed (GM-8)I get 14/15 lbs boost until it upshifts then 20/22 is the norm, w/egt's staying safe.

If I leave the manual "heath" gate controller set to say 14lbs boost my egt's (pre-turbo) climb into unsafe zone. I'm thinking this is due to the hi-pop injectors along w/maxitorq programming.